• Journal of the Korean Society of Radiology
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• v.13 no.3
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• pp.445-451
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• 2019

The fluorescence intensity and fluorescence lifetime of $Ba_2GdV_3O_{11}$, a vanadate compound based on $Ba^{2+}$ ion, were investigated by adding $Eu^{3+}$ as a rare earth ion which is an alkaline earth metal, which is distributed around active ions and has a large influence on fluorescent properties when used as a host in a phosphor. $Ba_2GdV_3O_{11}:Eu^{3+}$ phosphor was synthesized by solid state method and the crystallinity of the phosphor was confirmed by X - ray diffraction analysis. The fluorescence properties of the $Ba_2GdV_3O_{11}:Eu^{3+}$ phosphor were measured using optical and laser. The energy transfer and diffusion of the $Ba_2GdV_3O_{11}:Eu^{3+}$ phosphor are highly dependent on the concentration of $Eu^{3+}$. When the concentration of $Eu^{3+}$ is low, it shows strong fluorescence to the CT band. However, as the concentration of $Eu^{3+}$ increases, the fluorescence due to 4f - 4f transition is strong. The concentration of $Eu^{3+}$ ion increased and the energy between ions was diffused, and the lifetime of fluorescence decreased. Energy transfer occurs between two $Eu^{3+}$ ions at low $Eu^{3+}$ concentration and energy diffusion occurs at high $Eu^{3+}$ concentration.

• Journal of the Korean Ceramic Society
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• v.41 no.8
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• pp.573-577
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• 2004

We have synthesized a Eu$^{2＋}$-activated Sr$_3$MgSi$_2$ $O_{8}$ blue phosphor and investigated an attempt to develop blue LEDs by combining it with a InGaN blue LED chip (Len=405 nm). The InGaN-based Sr$_3$MgSi$_2$ $O_{8}$：Eu LED Lamp shows two bands at 405 nm and 460 nm. The 405 nm emission band is due to a radiative recombination from a InGaN active layer. This 405 nm emission was used as an optical transition of the Sr$_3$MgSi$_2$ $O_{8}$：Eu phosphor. The 460 m emission band is ascribed to a radiative recombination of Eu$^{2＋}$ impurity ions in the Sr$_3$MgSi$_2$ $O_{8}$ host matrix. As a consequence of a preparation of W blue LED Lamp using the Sr$_3$MgSi$_2$ $O_{8}$：Eu blue phosphor, the highest luminescence efficiency was obtained at the ration of epoxy/blue phosphor(1/0,202). At this time, the CIE chromaticity was x=0.1417 and y=0.0683.

• Journal of the Korean Chemical Society
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• v.45 no.6
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• pp.577-588
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• 2001

Eu doped YRO$_4$ (R=As, Nb, P, V) red phosphors were prepared by the combinatorial chemistry method. The quaternary material library of tetrahedron-type composition array was designed to investigate the luminescence of the host material under UV and VUV excitations (254, 147 nm). The photoluminescent characteristics of the samples were comparable to the commercially available red phosphors such as (Y, Gd)BO$_3$: $Eu^{3+}$ and Y$_2$O$_3$: In view of the luminescence yield, V rich region was found to be optimum under UV excitation. But the results under VUV excitation were different from those of UV excitation, the samples of the composition containing a large amount of P shows the highest luminescence. Especially, higher luminescence was obtained in $Y_{0.9}$(A$S_{0.06}$N$B_{0.06}P_{0.83}V_{0.06}$) O$_4$: $Eu_{0.1}$ phosphors than commercial (Y, Gd)BO$_3$red phosphors under 147 nm excitation.

• Korean Journal of Materials Research
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• v.10 no.1
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• pp.49-54
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• 2000

The new green $Al_3GdB_4O_{12}:Tb^{3+} and red Al_3GdB_4O_{12}:Eu_{3+}$ phosphors were synthesized and then characterized their optical properties for PDP application. And also the photoluminescence properties of these phosphors were compared with the commercial green $Zn_2SiO_4:Mn^{2+} and (Y,Gd)BO_3: Eu^{3+}$ red PDP phosphors. The phosphors were synthesized by solid state reaction at 115$0^{\circ}C$ for 4hr. It was found that the emitting brightness of $Al_3GdB_4O_{12}:Tb^{3+}$(15mol%) green phosphor under 147nm excitation was higher than that of commercial $Zn_2SiO_4: Mn^{2+}$ green PDP phosphor. However, the color coordinate of this new green phosphor was inferior to the commercial one. On the other hand, the emitting intensity of $Al_3GdB_4O_{12}:Eu^{3+}$(15mol%) red phosphor was smaller than the $commercial(Y,Gd)BO_3: Eu^{3+}$ red one, but the CIE coordinate was slightly improved. The excitation spectrum showed that $Al_3GdB_4O_{12}$ phosphors had a strong excitation band at $\lambda=160nm$ associated with the host absorption. And the photoluminance excitation (PLE) intensity in VUV range for $Al_3GdB_4O_{12}:Tb^{3+}$ green phosphor was higher than that of $Zn_2SiO_4: Mn^{2+}$, but the PLE intensity of $Al_3GdB_4O_{12}:Eu^{3+}$ red phosphor was smaller than $(Y,Gd)BO_3: Eu^{3+}$.

• Journal of the Korean Society of Radiology
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• v.17 no.1
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• pp.17-23
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• 2023

In this study, the thermoluminescence kinetics of electron trap in Li₆Y_0.5Gd_0.5(BO₃)₃ (LY_0.5G_0.5BO) scintillator for neutron detection composed of Li, Gd, and B with a high neutron response cross-section were investigated. The thermoluminescence glow curve of the LY_0.5G_0.5BO scintillation single crystal was measured and analyzed using the peak shape method, the initial rise method, and the machine learning algorithm to evaluate the physical parameters of the electron trap. The glow curve of the LY_0.5G_0.5BO scintillation single crystal consisted of a single peak. As a result of analyzing this peak, the activation energy, emission order, and frequency factor of the electron trap were 0.61 eV, 1.1, and 1.7×10⁷ s^-1, respectively. In addition, the possibility of thermoluminescence analysis of scintillators using machine learning was confirmed.

• Journal of the Korean Society of Radiology
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• v.9 no.1
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• pp.39-45
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• 2015

$La_2W_3O_{12}:Eu^{3+}$ phosphors were prepared by solid state reaction method. The crystal structure was characterized by XRD pattern and ICSD card (78180). Luminescence properties of $La_2W_3O_{12}:Eu^{3+}$ are investigated by optical and laser-excitation spectroscopy in which emission and excitation spectra and time-resolved spectra are measured. The 1 mol % $Eu^{3+}$-doped $La_2W_3O_{12}$ phosphor exhibits broad excitation band peaking at 286 nm due to the ligand-to-metal charge transfer transition. The excitation lines due to the $^7F_0{\rightarrow}{^5D_4},{^5D_4},{^5L_6},{^5G_4},{^5D_3},{^5D_2}$ transitions of $Eu^{3+}$ are observed in the wavelength region 350-500 nm. The strong line emission is observed at 618 nm corresponding to the due to the $^5D_0{\rightarrow}^7F_2$ transition. The lifetime of 618 nm emission decreases with increasing temperature as 7 K ($114{\mu}s$), 100 K ($94{\mu}s$), 200 K ($10{\mu}s$) and 300 K ($0.5{\mu}s$).

• Journal of radiological science and technology
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• v.29 no.3
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• pp.141-145
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• 2006

In this study, $Eu^{2+}$ ion was used as an activator in order to enhance the PL(photoluminescene) and PSL(photostimulated luminescence) intensity of $MCl_2:Eu^{2+}$(M = Ca, Sr, Ba)phosphors and the chracteristics of PL and PSL of the phosphors were investigated. The emission of $MCl_2:Eu^{2+}$(M = Ca, Sr, Ba) phosphors shows a shift wavelength when the host caution changes. The optimal preparing conditions of $CaCl_2:Eu^{2+}$ phosphor were 0.5 mol％ of $EuCl_2$ and the sintering temperature were $745^{\circ}C$, 45 min. in $H_2$ atmosphere. The PL and PSL spectra of $CaCl_2:Eu^{2+}$ locate in the range of $365{\sim}388\;nm$, peaking at 370 and 380 nm. The optimal preparing conditions of $BaCl_2:Eu^{2+}$ phosphor were 0.5 mol％ of $EuCl_2$ and the sintering temperature were $905^{\circ}C$, 45 min. in $H_2$ atmosphere. The PL and PSL spectra of $BaCl_2:Eu^{2+}$ locate in the range of $370{\sim}460\;nm$, peaking at 398 nm. The optimal preparing conditions of $SrCl_2:Eu^{2+}$ phosphor were 0.5mol％ of $EuCl_2$ and the sintering temperature were $840^{\circ}C$, 45min. in $H_2$ atmosphere. The PL and PSL spectra of $SrCl_2:Eu^{2+}$ locate in the range of $380{\sim}440\;nm$, peaking at 407 nm. The dose response of the $MCl_2:Eu^{2+}$(0.5 mol%)(M = Ba, Sr) phosphors were linear within $0.25{\sim}200\;mGy$ of 100 kV X-ray and the PSL intensity of the $SrCl_2:Eu^{2+}$ and $BaCl_2:Eu^{2+}$ phosphors faded to approximately 60 and 40% respectively after 120 min at room temperature.

• New Physics: Sae Mulli
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• v.68 no.11
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• pp.1196-1202
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• 2018

$Li_2Sr_{1-x}Eu_xSiO_{4-{\alpha}}N_{\alpha}$ ($Li_2SrSiO_{4-{\alpha}}N_{\alpha}:Eu^{2+}$) phosphors were synthesized by using a solid state reaction (SSR) method with submicron $Si_3N_4$ and nano $Si_3N_4$ powders as the sources of Si and N, and the optical properties of those phosphors were studied. The studied phosphors showed efficient excitation characteristics over the broad range from 230 to 530 nm. Also, They showed broad emission spectra covering a range from 500 to 700 nm, with a peak at 568 nm, which was shifted longer wavelength by 18 nm as compared with that of commercial $YAG:Ce^{3+}$. Combined with a 450 nm blue LED chip, the results support the application of the $Li_2SrSiO_{4-{\alpha}}N_{\alpha}:Eu^{2+}$ phosphor as a luminescent material for a white-light source thaat is warmer than the commercial $YAG:Ce^{3+}$ white-light source. In addition, the $Li_2SrSiO_{4-{\alpha}}N_{\alpha}$ phosphors prepared from a submicron $Si_3N_4$ powder was found to emit a previously unreported self-activated luminescence in $Li_2SrSiO_{4-{\alpha}}N_{\alpha}$.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.37 no.1
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• pp.29-35
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• 2000

Luminescent characteristics of SrS:Cu,X TFeL devices fabricated by electron-beam deposition system were studied. The SrS powders were used as the host materials and Cu, $CuF_2,\;Cu_2S$ or CuCl powders were added as the luminescent center. The emission spectra of the SrS:Cu,X TFEL devices strongly depended on coactivators. The luminance($L_{40}$) and efficiency(${\eta}_{20}$) of SrS:$Cu_2S$ TFEL device were 1443 cd/$m^2$ and 2.44 lm/w, respectively. Green color was observed from this TFEL device. The luminous efficiency of SrS:$Cu_2S$ TFEL device was higher than that of ZnS:Tb TFEL device, and it also could be good green phosphors for TFEL devices. The luminance($L_{40}$) and efficiency(${\eta}_{20}$) of SrS:CuCl TFEL device were 262 cd/$m^2$ and 0.26 lm/w, respectively. Blue color was emitted from this TFEL device.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.18 no.1
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• pp.22-26
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• 2008

Red long persistent phosphors of $CaZrO_3$ : Pr was synthesized by a solid reaction method. $CaCO_3\;and\;ZrO_2$ were used as hosting materials and Pr was doped as luminescence center element, and $B_2O_3$ was used as flux. The XRD pattern confirmed crystalline phase of the phosphor, and photoluminescence investigation showed emission spectrum at $480{\sim}570nm\;and\;590{\sim}700nm$. Phosphor samples were synthesized with $B_2O_3$ flux concentration of 1, 5, 10%, and luminescent peak of maximum intensity at 494 nm was obtained for 1% $B_2O_3$. Luminescent peak of red color at 620 nm was of highest intensity for 10% $B_2O_3$.